1. Field of the Invention
The present invention relates generally to hearing devices and, more particularly, to anchoring elements for bone anchored hearing devices.
2. Related Art
For persons who cannot benefit from traditional, air conduction hearing aids there are other types of hearing aids on the market commonly referred to as bone anchored hearing aids. Bone anchored hearing aids mechanically transmit sound information to a person's inner ear via the skull bone by means of a vibrator. Such hearing aid devices are typically connected to a percutaneous implant in the form of a titanium screw implanted in the skull bone behind the external ear so that sound is transmitted via the skull bone to the cochlea (inner ear). This enables the hearing aid to be effective regardless of whether there is disease or damage in the middle ear. Moreover, penetration of the skin makes the vibratory transmission very efficient.
Bone anchored hearing aids were initially developed to rehabilitate certain types of hearing-impaired patients. They may also be utilized for other indications such as stuttering and for certain non-medical applications. A bone anchored hearing aid may be connected to an implant by means of a bayonet coupling, a snap-in coupling, a magnetic coupling or the like. One example of this type of hearing aid device is the BAHA® bone anchored hearing aid, described in U.S. Pat. No. 4,498,461 and commercially available from Cochlear Bone Anchored Solutions AB (previously Entific Medical Systems AB) in Göteborg, Sweden.
The implant connecting the hearing aid to the skull generally comprises two components: a bone attachment piece that is attached or implanted directly into the skull bone and a skin penetrating piece coupled to the bone attachment piece. The reason for this two-piece design is that installation of the implant is occasionally performed in two steps. In the first step, the bone attachment piece is installed and the surrounding issue is allowed to heal for a period of time that may last up to a few months. In the second step, the skin penetrating piece is coupled to the bone attachment piece. In the event that the skin penetrating piece becomes damaged, it may be replaced without removing the anchoring fixture from the skull. Moreover, the hearing aid may be changed or upgraded if necessary, without removing the bone attachment piece from the skull.
Although conventional fixtures normally provide a certain degree of osseo-integration, a more effective integration between the implant screw and the skull bone is desired, for example, for patients having impaired bone quality. Moreover, loading of the implant at an earlier stage would also be desired.